The invention also relates to a key for a locking device.
DE 298 18 143 U1 describes a safety key and the tumbler pin of an associated locking cylinder. The broad side face of the flat key shank of the safety key has a multiplicity of cup-shaped coding recesses. Each coding recess has a supporting flank, which is formed by the bottom of the cup and on which the blunt end of a tumbler pin beveled at the tip can be supported. The supporting surface merges into a concavely rounded sliding surface. This rounding merges into a more inclined sloping flank. The latter merges into a concavely rounded sliding surface with a smaller slope. The concavely rounded sliding surface runs out in a broad side face of the key shank. This produces a shape of a sliding flank without any points of inflection and with portions inclined to differing degrees with respect to the direction of insertion of the key into the key channel of the locking cylinder.
A coding recess with a sliding flank of a shape without any points of inflection and with portions sloping to differing degrees is also described by DE 20 2006 005 188 U1. Here, the wall of the coding recess is formed by an arcuate portion produced by the use of a circular milling cutter with a constant milling radius.
DE 10 2004 021 580 B3 describes a flat key with coding recesses with straight sliding flanks. The flanks of adjacent coding recesses merge into one another while forming an acute angle. The apex angle of the two sliding flanks forming a coding recess is approximately 106°. The apex angle is preferably greater than 90°, in order to keep down the force component acting in the horizontal direction during the withdrawal of the key from the key channel. The shallower the angle of the sliding flank, the smaller the forces in the horizontal direction that are required to move the tumbler pins in the axial direction. Shallow sliding flanks have the disadvantage, however, that directly adjacent coding recesses can only have a relatively small difference in their depth of incision. The coding of a flat key is achieved by sliding flanks cut to different depths. The sliding flanks may meet at a point of intersection, as is the case for example in DE 10 2004 021 580 B3. The sliding flanks may, however, also merge into a supporting flank, as is the case with DE 298 18 143 U1. When the key is pushed into the key channel of a locking cylinder, a tumbler pin is made to enter an allocated coding recess. The tumbler pins are of different lengths, the depth of insertion of the associated coding recess being adapted to the length of the respective tumbler pin in such a way that, when the key is completely pushed in, the tumbler pins do not protrude beyond the shear line of the locking cylinder into a driver pin hole and driver pins mounted in the driver pin hole do not protrude into the core pin hole.
In order to increase the variety of permutations, the maximum differences in the depths to which adjacent coding recesses are cut must be as great as possible. With shallow sliding flanks, this requires adjacent tumbler pins to be spaced far apart in the direction of extent of the key channel. This would increase the overall length of the locking cylinder, which is undesired. If, for example, the slope of the sliding flanks is increased to 90°, the force component acting in the direction in which the key is withdrawn, that is to say in the direction of extent of the key channel, at the same time becomes greater. This may lead to a tumbler pin jamming within the pin hole.